Corneal scars limit vision for hundreds of millions of persons worldwide. Scarring has a diverse etiology but is usually permanent and correctable only by surgery. The long-range goal of this research to determine the physical and biological properties of corneal scar tissue and the conditions that control its formation. Proteoglycans constitute a major component of the stroma and proper proteoglycan composition appears essential for corneal transparency. There is a marked alteration in the proteoglycan composition of scar tissue compared to that of normal tissue; however, the nature of scar proteoglycans is not well defined. A model is presented proposing roles for proteoglycans in the biology of scar tissue based on our current knowledge of extracellular matrix biology. Experiments, testing hypotheses based on this model, are designed to accomplish four specific aims: (1) Compare proteoglycans of normal and scarred human corneas in terms of proteoglycan molecular types. (2) Define specific interactions between corneal proteoglycans and other biochemical components of the corneal extracellular matrix. (3) Examine the biological activity of proteoglycans (4) Determine factors regulating scar tissue synthesis by keratocytes. For the first aim, antibodies will be used to determine the abundance and identity of proteoglycan protein cores in histological sections and in extracts of scarred human corneas. Lectins and antibodies against the carbohydrate portions of these molecules will be used to define their state of glycosylation. In aim 2 & 3, purified proteoglycans, representative of those identified in scarred and normal stroma, will be examined for specific interactions with extracellular matrix molecules and with cells of scar tissue. Effect of the state of glycosylation and of specific amino acid sequence in the core protein will be assessed by use of deglycosylated proteins and of recombinant-proteins containing portions of the core proteins. Interactions will be examined with collagens, laminin, transforming growth factor beta, keratocytes, and macrophages, assessing proteoglycan binding and the biological effects of the binding. In the fourth aim, a soluble factor affecting keratocyte function will be purified and characterized. These experiments will provide knowledge essential to our understanding of corneal scar biology and to our ability to control this pathological process.